Stratigraphy and conodonts of the Lower Carboniferous of the Shishkat section (southern Tien Shan, Tajikistan)

Abstract

The Shishkat section, on the northern slope of the Zeravshan range, with its continuous sequence from the middle Silurian up to the middle Carboniferous is unique in Central Asia because of its Devonian-/Carboniferous boundary deposits. The Carboniferous is represented by layered limestones in upper part of Surkhobi Formation and by massive limestones in Yura Formation. The study of the vertical conodont distribution has allowed to subdivide the deposits into the following conodont zones:praesulcata, sulcata, Lowerduplicata, Upperduplicata, sandbergi, Lowercrenulata, Uppercrenulata, typicus, anchoralis-latus, texanus, commutata, bilineatus and?nodosa. In the upper Yura Formation, the Middle Carboniferous conodontsDeclinognathodus sp.,Idiognathodus delicatus andIdiognathoides asiaticus occur. No conodont zone younger than the?nodosa Zone, however, could be recognized in the upper Yura Formation because of the poor conodont contents. The conodont zones are correlated with foraminifera zones which are established in the section. The following new taxa are described:Ctenopolygnathus jalilovi sp. nov.,Eucostapolygnathus lidiae sp. nov.,Laterignathus aristovi sp. nov.,Scaliognathus? chirkini sp. nov.,Siphonodella praeplana sp. nov.,Siphonodella wilberti sp. nov.